The goal of this proposed research is to elucidate the factors which regulate adipocyte number and size in various mammals including man. The problem relates to the pathogenesis of human obesity which occurs in hypercellular, hypertrophic, and mixed forms. Obesity often contributes to the pathogenesis, severity, and complications of diabetes mellitus, hypertension, and hyperlipidemia. The approach proposed here is to adapt the technique of tissue culture to investigation of this problem. Immediate objectives are to establish optimal conditions for adipocyte culture, to prove that the cultured cells derive from adipocytes, and to prove that the cultured cells are capable of differentiating into adipocytes. Long term objectives include establishing a human preadipocyte line, to compare the growth rates and other properties of cells derived from obese and non-obese humans and experimental animals, and to study the effects of hormones and nutrients on these parameters.